Field of the Invention
The invention relates to an electronic control unit for an automatic transmission of a motor vehicle and a method for adjusting a position detection sensor in the automatic transmission of the motor vehicle.
Automatic transmissions for passenger cars are usually electronically controlled. The control units for this purpose have hitherto been provided as so-called xe2x80x9cstand-alone unitsxe2x80x9d in a control box that protects against environmental influences, or have been directly installed in the passenger space of the vehicle. Recently, for reasons of cost and quality, a new approach of integrating the electronic control system and an associated sensor system directly into the automatic transmission has been adopted. Fundamental requirements for the operation of the electronics in the transmission are the operational capability over a wide temperature range, for example xe2x88x9240xc2x0 C. to 140xc2x0 C., tightness with respect to ATF transmission oil and sufficient resistance to vibration, for example 30 g. Optimized temperature resistance is obtained by bonding the electronic circuit on a ceramic substrate with a heat conducting adhesive onto a metal baseplate, for example made of aluminum.
In addition to rotational speed sensors, pressure sensors and temperature sensors, customary transmission controllers for automatic transmissions have a position detection sensor that is used to sense which driving position of the automatic transmission is set. The latter is carried out, for example, by setting a so-called selection position switch to one of xe2x80x9cPxe2x80x9d (=Park), xe2x80x9cRxe2x80x9d (=Reverse), xe2x80x9cNxe2x80x9d (=Neutral) or xe2x80x9cDxe2x80x9d (=Drive) positions. The selection position switchxe2x80x94also referred to below as a selector leverxe2x80x94is mechanically connected to the automatic transmission by activating a selector slide that can move in a linear or rotary fashion. The selector slide is incorporated into the hydraulic part of the transmission controller. As a result of the sensing of the selector slide position by the position detection sensor, the drive position which has been set is communicated to the electronic control unit.
In terms of the position detection, it is then known to provide an independent sensor that is packed in an oil-tight fashion in a housing in order to protect against the surrounding medium, namely transmission oil. The electrical connection of the sensor using appropriate leads to the control unit must also be of an oil-tight configuration.
Various measurement principles are conceivable for the configuration of the sensors. German Patent DE 196 03 197 C1 discloses the use of magnetic field sensors which are based on the Hall effect. In such configurations the measurement quality is influenced considerably by an air gap between the magnet and the sensor element. For this reason, a trigger element (PES slide) which is embodied as a slide and in which an encoded magnetic plate or a signal transmitting magnet is integrated is guided with precise tolerances in guide grooves of the sensor housing. The selector slide, which is internal to the transmission and which is connected rigidly to the selector lever in the interior of the vehicle via a linkage or a Bowden cable, engages in the PES slide. If the selector lever is moved from one position into another, the moveable PES slide is also adjusted by the selector slide in the transmission, with the result that the electronic system of the transmission can input the new selector lever position.
Position detection sensors based on the Hall effect are, like position detection sensors that are based electromechanically on the switch or slide principle, of exclusively digital configuration. The absolute accuracy of the system obtained depends on a chain of tolerances of the electronic and mechanical components involved. It is no longer necessary to perform static correction after installation in the vehicle or transmission, or to perform dynamic correction during operation.
It is accordingly an object of the invention to provide an electronic control unit for an automatic transmission of a motor vehicle and method for adjusting a position detection sensor in the automatic transmission of the motor vehicle that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electronic control unit for an automatic transmission of a motor vehicle, the electronic control unit including a fluid-tight housing; an electronic control system accommodated in the housing; and a position detection sensor for sensing a position of a selector slide. The position detection sensor supplying an analog output signal that is dependent on the position of the selector slide, and the position detection sensor is dynamically adjusted using a self-learning algorithm stored in the electronic control system during operation of the motor vehicle.
The invention is based on the technical problem of incorporating the position detection sensor into an electronic control unit with a high degree of accuracy in a simple and cost-effective way, and of providing a method which permits the sensor to be adjusted during operation in the vehicle.
In addition to digital (Hall sensor) sensor principles, analog ones, for example on the basis of a permanent magnetic linear contactless displacement (PLCD) sensor, are also known for position detection sensors. A PLCD is based on a coil configuration that contains an integrated electronic evaluation circuit, for example as an ASIC module, and generates an analog signal, preferably a voltage signal, on the basis of the position of signal transmitting magnets relative to the sensor. Such a module is marketed by Siemens, for example.
In position detection sensors, the accuracy with which the selection positions (P, R, N or D) can be sensed is a decisive quality feature. In contrast to digital position detection sensors, in analog position detection sensors it is possible to adjust the sensors statically or dynamically in order to increase the accuracy in the system. If a self-learning algorithm is used for this purpose, the sensor can be adjusted completely automatically during operation in the vehicle. In this way, installation tolerances and aging effects of the position sensor in the transmission are largely eliminated.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electronic control unit for an automatic transmission of a motor vehicle and method for adjusting a position detection sensor in the automatic transmission of the motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.